Squashed commit of the following:

sched/semaphore:  Add nxsem_post() which is identical to sem_post() except that it never modifies the errno variable.  Changed all references to sem_post in the OS to nxsem_post().

    sched/semaphore:  Add nxsem_destroy() which is identical to sem_destroy() except that it never modifies the errno variable.  Changed all references to sem_destroy() in the OS to nxsem_destroy().

    libc/semaphore and sched/semaphore:  Add nxsem_getprotocol() and nxsem_setprotocola which are identical to sem_getprotocol() and set_setprotocol() except that they never modifies the errno variable.  Changed all references to sem_setprotocol in the OS to nxsem_setprotocol().  sem_getprotocol() was not used in the OS

audio/audio.c

@@ -178,7 +178,7 @@ static int audio_open(FAR struct file *filep)
   ret = OK;
 
 errout_with_sem:
-  sem_post(&upper->exclsem);
+  nxsem_post(&upper->exclsem);
 
 errout:
   return ret;
@@ -235,7 +235,7 @@ static int audio_close(FAR struct file *filep)
   ret = OK;
 
 //errout_with_sem:
-  sem_post(&upper->exclsem);
+  nxsem_post(&upper->exclsem);
 
 errout:
   return ret;
@@ -657,7 +657,7 @@ static int audio_ioctl(FAR struct file *filep, int cmd, unsigned long arg)
         break;
     }
 
-  sem_post(&upper->exclsem);
+  nxsem_post(&upper->exclsem);
   return ret;
 }